The use of liquid crystal cells (LCC) for the diffusion of light is well known in the field of optics. Assouline, U.S. Pat. No. 3,718,381, Peterson, U.S. Pat. No. 3,937,561 and Sinclair, U.S. Pat. No. 4,364,639, all disclose various uses and arrangements for the diffusion of light by LCC's.
In addition, Proske, U.S. Pat. No. 4,323,952, discloses an LCC lens arrangement which provides instantaneous light diffusion for camera flash equipment. Proske's arrangement is comprised of a reflector cone, a light source and an LCC lens. In this arrangement, the LCC covers the entire open end of the reflector, so that the diffusing element is positioned in a path between the light source and the object to be illuminated. Proske also provides a means whereby the diffusion level can be changed by varying the voltage which is applied to the lens.
There are several disadvantages to this arrangement. First, since the configuration employs a rapidly dissipating light source (flashbulb) in the reflection system, illumination occurs so rapidly that it can not be accurately sensed by the eye. As a result, the instantaneous diffusion, caused by the lens, is beneficial only when using a film-sensitive device such as a photographic camera. Secondly, the LCC must be large enough to cover the entire front opening of the reflector. Since the cell is large, it is expensive to manufacture and replace. This is especially disadvantageous since the LCC is exposed to being damaged, especially in a working environment. And finally, since the LCC is used as a front lens, the light rays are diffused only as they leave the reflector. Thus, only a moderate degree of light control is possible.